Automatic blade angle control for helicopters



Jan. 13, 1953 l. B. LASKOWITZ AUTOMATIC BLADE ANGLE CONTROL FOR HELI'OOPTERS Filed Jan. l2, 1948 .1N VEN TOR. V LaJ/To wi Patented Jan. 13, 1953 gif 2,625,228 AUTOMATIC BLADE ANGLE CONTROL FOR HELICOPTERS.;

Isidor B. VLaskowitz, Brooklyn, N. Y. Appunti@ January 12, 194s, serial No. 2,036

6 Claims. (Cl. HUA-135.27)

This invention relates to automatic blade angle controls for helicopters, and embodies certain improvements in the Tiltable Counter-Rotating Rotor System for Helicopters and Control Means Therefor, fully described and claimed in the United States Letters Patent N-o. 2,434,276, granted to me January 13, 1948.

It is a primary object of this invention to provide mechanism whereby the pitch angles of the blades of the rotor or rotors of helicopters may be automatically increased or decreased as the speed of the engine or motor increases or Vdecreases and so eliminate the need for manually reducing the pitch angles of the blades to that required for autorotation should the engine or motor fail and for otherwise varying the pitch angles of the blades for their most efficient operation and preventing stalling of the engine due to overload.

Another important object of the invention is to embody the features of mechanisms having the qualities set out above whi-ch will be relatively simple in construction yet positive in action,

strong and durable with parts arranged to facil-v itate ready and easy adjustments whenever necess-ary, thus assuring its practicability.

Other objects and advantages of the present invention will become apparent from theY following detailed description of preferred embodiments of the invention illustrated inthe accompanying drawings wherein like referencecharac-V ters design-ate corresponding parts throughout the several views and wherein:

Figure 1 is a vertical section taken substantially in a plane indicated by the line I-I of Fig. 2 embodying the invention, sho-Wing an arrangement for the operation of the lever to automatically change the pitch angles of the blades of the spars I by means of ball or roller bearings 8.l

Secured to the upper blades I and to the lower blades I', at theirvinner ends, are the arms I4,

each arm terminating with an antifriction roller,y

I5. The rollers I5 through the action of the springs I6, on the arms I4, aid in keeping the rollers I5 in physical contact with the blade pitch angle changing cones or cams Il and I8.l Thus,

. 2 when rotating,rthe pitch angles or angles of incidence of the blades of the upper and lower rotors depend on the position of the cones II and I8, respectively.

In the drawing the arms M are provided with upright portions and horizontal portions. In Fig. 1 the horizontal portions of the arms, upper right' and lower left, lare broken off sofas to depict clearly the cross section of the cones or cams Il and I8. The Aother horizontal portions, upper left and lower right, have their terminals concealed back of the cone orycam construction. None of the terminalv antifriction-rollers I5`are disclosed in Fig. 1,'but in Fig. 2 the upper antifriction rollers I5 are shown in contact with the cone or cam construction. Rotor blade pitch angle changing cones Il and I8 arecarried by the cylindrical support or tubular stai 48 and is slidably mounted on the neck portion of the tubular shaft or stud 49 of the eccentric bracket 36.

An intermediate' steady bearing 32 is provided forshaft 20,vr and isV mounted on frame member 35. lvearing32 also serves to give additional supportto theeccentric'bracket 36.

The usual effect lof raising the staff or support 48 is to simultaneously increase the pitch angles of the blades ofthe rotors and consequently toV increase the lift or thrustv of the rotors. Lowering the Vsupport 4B has the reverse effect. The eccentric bracket or support 36 is horizontally movable in any direction ofthe compass. For such a construction attention is called to myV application Serial No. 471,492v ledJanuary 6l943, for Variable Thrust Mechanism nowl Patent Number 2,434,276, granted to me January 13, 1948. v I t The Vlower end of the cylindrical supporter staff 48 is carried by means of the pins 5I on the lever 52 which is pivotally mounted on the pin 53 between the brackets 54 secured tothe eccentric bracket 36.

. The levery 52 for .simultaneously changing the:

pitch anglesof the .blades is not extended within reach of the pilot, instead--the lowerend of the lever 52 engages the 'pivoted end |15 of tuepis-nn rod IIE secured to apiston II6A,-Whi=ch slides in the cylinder II'I. i Cylinder II'I isp-ivotally'sup;

ported at one end by means ofthe pin lIII! and* the bracket I Irwhich secured to the eccentric bracket 36.

Y Upper and lower limitstops |23 are provided. for limiting the movement of the lever 52.

springv |24 creates a pulloil 161782,52 tending to;

bringthe lever 52 in its lowestposition vand. 0011.-;

sequently the smallest pitch angle setting for the blades of the rotor or rotors. Pivoted end of the cylinder is open to the atmosphere through the vent the other end of the cylinder is connected by means of the flexible pipe |20 to a pump or compressor |25 of the centrifugal type. The p-ump |25 is connected by means of the shaft |26 and the bevel gears |21 to the drive shaft 21| of the engine orl motor 25. An automatic declutching or free-wheeling device 33 of any suitable or preferred type is interposed between the engine or motor 25 and shafts t8 and 20, whereby these shafts and the rotors mounted thereon are free to rotate when the engine or motor is notr functioning. An oil or other fluid-reservoir |28V is connected to the intake of pump |25. Since the pump |25 is directly connected to the kengine 25 the speed of the pump will vary as the speed of the engine or motor. A by-pass |29connects the suction pipe of the pump to the flexible pipe |2|l. A relief valve |30 set at any predetermined relief `pressure is inserted in the by-pass line |29.

The gears |21 on the shafts 24 and |26 are maintained in position by the inverted U-shaped bracket |21' which is secured to the oor of the frame 26. The tank |28 and its depending pipe are maintained in position by the bracket arm |28. The brackets |21 and |283' together maintain the shaft' |26 in a'steady upright position.

Thus, as the engine or motor 25 rotates, pump |25 will also operate and create a pressure in the pipe |20, which pressure will actuate the piston ||6A in the cylinder and move the lever 52 which in turn will raise the support 48 to increase the pitch angles of the blades against the action of the spring |24. As the speed of the engine 25A is increased or decreased, the pressure created by the pump |25 will also be increased ordecreased and as a result lever 52 will be raised or lowered and automatically increase ordecrease the pitcnangles of the blades. Since the speed ofthe engine 25 is controlled by itsv throttle the variation in the pitch angles of the blades will automatically vary with the setting of the throttle. And for any position of the throttle VshouldV the engine fail, the lever 52 will be yautomatically lowered to decrease the pitch angles ofthe blades for a safedescent of the craft.

Obviously, minor changes may be made in the preferred embodiment without departing from the essence of the invention or'the scope' ofthe appended claims. Thus, ball -or roller bearings may be employed in place of the sleeve bearings disclosed. It is contemplated that other equivalent mechanical, hydraulic or electrical control movements might be substituted for the vone shown without essentially-departing from the scope-of the invention as claimed.

Having fully disclosed my invention, what I claim is:

1. InY a coaxial helicopter construction, an automatic blade pitch angle control mechanism, said mechanism comprising a support having an upright hollow stud thereon, a tubular supporting staff, blade pitch angle changing cones mounted on said staff, an upright bracket and a depending bracket -on said support, a bellcrank lever, a piston, piston rod and cylinder, a pump and fluid reservoir or chamber, a prime mover, said' lever beingy pivotally mounted in said upright bracket and having one end pivotally connected to said tubular staff and its otherend pivotally connectbeing pivotally connected to the depending bracket, the piston rod end of said cylinder having ilexible yieldable tubular uid connection with said pump, said pump having operative mechanical connection with said prime mover whereby said pump may be operated, said chamber having tubular fluid connections with said pump, said staff being movably and telescopically connected to said hollow stud,.the pivoted end of said cylinder having a vented portion, and means for moving said cones automatically to their lowest position, should the prime mover fail.

2l In ar helicopter construction, a pressure operated means to automatically control the angular pitchof the rotor blades, said construction comprising a substantially horizontal support, a bell crank lever pivotally mounted on and above said horizontal support, a cylinder pivotally mounted on and below said horizontal support. a piston and piston rod operatively associated with said cylinder, in combination with fluid pressure means for actuating said piston, said last named means having iiuid connection and communication with said cylinder, an upright hollow stud on and projecting upwardly from said horizontal support, an upright movable tubular support telescopically receiving said stud, blade pitch angle changing cones mounted on said tubular support, one end of said bell crank lever being pivotally connected to the free end of said piston rod and its other end pivotally connected to the upright support whereby said upright support may be moved upwardly and downwardly telescopically on said stud, and means for moving said cones automatically to their lowest position should said fluid pressure means fail.

3. In a helicopter construction, an automatic blade pitch angle control mechanism, said mechanism comprising a movable support having a hollow upright stud, a movable hollow supporting means telescopically receiving said stud, 'blade pitch angle changing cones mounted on said hollow supporting means, an upright bracket and a depending bracket on said iirst named support, a bell crank lever pivotally fulcrumed in said upright bracket, a cylinder pivotally connected at one end to the depending bracket and having a reciprocating piston therein, a pump, a fluid chamber, a motor, a tubular connection having a yieldable and flexible portion therein establishing fluid communication between the cylinder and said pump, operative connections between the motor and the pump for actuating the latter, one end of said bell crank lever being pivotally connected to the reciprocating piston, a tubular bypass connecting the fluid chamber and said tubular connection leading to the cylinder, said cylinder having a vented portion located in the pivoted end of the cylinder.

4. In a helicopter, a frame, counter-rotating shafts arranged vertically on said frame, a pair of rotors, each comprising a hub and a plurality of blades, said hubs being mounted on said counter-rotating vertical shafts, said blades being rotatable'about their longitudinal axes, a pair of cones encircling -said shafts and operatively connected to the blades, an engine operatively connected to said shafts, fluid pressure means powered by said engine, reciprocating means actuated by said fluid pressure means, linkage connecting said reciprocating means and said cones for automatically moving said 'cones up or down as the speed of the'engine increases ordecreases to simultaneously-varythe pitch angles of the blades of said rotors and moving said cones to their lowest position, should the engine fail, to reduce the pitch angle of Said blades to that required for auto-rotation.

5. In a helicopter comprising coaxial rotors having blades, 'blade pitch angle changing cones operatively connected to the blades whereby the pitch angle of the blade may be varied, an engine operatively connected to said rotors, a uid pump operatively connected to said engine, reciprocating means actuated by said fluid pump, linkage connecting said reciprocating means with said cones for automatically raising and lowering said cones for increasing and decreasing the pitch angle of said blades as the speed of said engine increases or decreases and l-owering said cones thereby reducing the pitch angle of said blades should said engine become inoperative` 6. In a helicopter comprising a plurality of coaxial rotors, each having movable blades, the pitch angle of which may be Varied, apair of blade pitch angle changing cones operatively connected to the blades, an engine operatively connected to said rotors, a fluid pump operatively connected to said engine. a cylinder, a reciprocating piston operable therein, said iiud pump being in communication with the cylinder to actuate the piston, spring actuated linkage operatively connected to said reciprocating piston and the cones for automatically varying the pitch angles of said blades simultaneously or collectively with variation in speed of said engine and to automatically lower said cones to reduce the pitch angle of said blades, to that required for autorotation, should the engine fail.

ISIDOR B. LASKOWITZ.

REFERENCES CITED The following references are of record in the le of this patent: 

